The canonical correlation analysis (CCA) forecast of
SST in the central Pacific (Barnett et al. 1988, Science, 241,
192‑196; Barnston and Ropelewski
1992, J. Climate, 5, 1316‑1345), is shown in Figs. F1 and F2. This forecast is produced routinely by the
Prediction Branch of the Climate Prediction Center. The
predictions from the National Centers for Environmental Prediction (NCEP)
Coupled Forecast System Model (CFS03) are presented in Figs. F3 and
F4a, F4b.Predictions from the
Markov model (Xue, et al. 2000: J. Climate, 13,
849‑871) are shown in Figs. F5 and F6.Predictions from the latest version of the
LDEO model (Chen et al. 2000: Geophys. Res.
Let., 27, 2585‑2587) are shown in Figs. F7
and F8.Predictions using linear inverse modeling (Penland and Magorian 1993: J.
Climate, 6, 1067‑1076) are shown in Figs. F9 and F10. Predictions from the Scripps / Max Planck
Institute (MPI) hybrid coupled model (Barnett et al. 1993: J. Climate, 6,
1545‑1566) are shown in Fig. F11.Predictions from the ENSO‑CLIPER statistical model (Knaff and Landsea 1997, Wea.
Forecasting, 12, 633‑652) are shown in Fig. F12.Niño 3.4 predictions are summarized in Fig.
F13, provided by the Forecasting and Prediction Research Group of the IRI.

The CPC and the contributors to the Forecast Forum caution
potential users of this predictive information that they can expect only modest
skill.

ENSO Alert System Status: El Niño Watch

Outlook:

There is an
approximately 50-60% chance of El Niño conditions during the next two months,
with ENSO-neutral favored thereafter.

Discussion:

During
December 2014, positive sea surface temperature (SST) anomalies decreased
across the central and east-central equatorial Pacific (Fig. T18). The monthly Niño indices ranged from+0.9°C in the
Niño-4 region, to +0.8°C in the Niño-3.4 region, to 0.1°C in the Niño-1+2
region (Table T2). The positive subsurface
heat content anomalies (averaged between 180º-100ºW) also decreased during
December in response to an upwelling equatorial oceanic Kelvin wave (Fig.
T17).Although
the surface and sub-surface temperature anomalies were consistent with El Niño,
the overall atmospheric circulation continued to show only limited coupling
with the anomalously warm water. The equatorial low-level winds were largely
near average during the month (Fig. T13), while upper-level
easterly anomalies continued in the central and eastern tropical Pacific (Fig.
T21). The Southern Oscillation Index (SOI) remained
slightly negative (Table T1), but the Equatorial SOI
remained near zero (Fig. T2). Also, rainfall remained
below-average near the Date Line and was above-average over Indonesia (Fig.
T25).Overall,
the combined atmospheric and oceanic state remains ENSO-neutral.

Similar to last month,
most models predict the SST anomalies to remain at weak El Niño levels (3-month
values of the Niño-3.4 index between 0.5°C and 0.9°C) during December-February
2014-15, and lasting into the Northern Hemisphere spring 2015 (Figs. F1-F13). If El Niño were to
emerge, the forecaster consensus favors a weak event that ends in early
Northern Hemisphere spring. In summary, there is an approximately 50-60% chance
of El Niño conditions during the next two months, with ENSO-neutral favored
thereafter.